Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. Emulsion aggregation toners may be used in forming print and/or xerographic images. Emulsion aggregation techniques may involve the formation of an emulsion latex of the resin particles by heating the resin using a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, 5,977,210, 5,994,020, and U.S. Patent Application Publication No. 2008/01017989, the disclosures of each of which are hereby incorporated by reference in their entirety.
Polyester EA ultra low melt (ULM) toners have been prepared utilizing amorphous and crystalline polyester resins as illustrated, for example, in U.S. Patent Application Publication No. 2008/0153027, the disclosure of which is hereby incorporated by reference in its entirety. The incorporation of these polyesters into the toner generally requires that they first be formulated into latex emulsions prepared by solvent containing batch processes, for example solvent flash emulsification and/or solvent-based phase inversion emulsification (PIE), which is time and energy-consuming.
In PIE, polyester resins may be converted into an aqueous dispersion by dissolving the polyester resin in at least one organic solvent which then needs to be removed, sometimes referred to as skipped, via a vacuum distillation process for safety and environmental concerns. However, due to both the presence of large amounts of solvents and a detrimental foaming phenomenon, i.e. formation of thick and long-life foam inside the distillation reactor, solvent stripping has become a very energy-intense and time-consuming step in PIE and can lead to product loss. For example, in a 300-gallon scale production, it takes about 6 hours and mild temperatures to produce the polyester dispersion whereas solvent stripping can take up to 30 hours under high temperature and high vacuum. To prevent any foam from boiling over (product loss), reactor vacuum level and temperature may be dropped to the point where solvent stripping efficiency is extremely slow.
Accordingly, it would be advantageous to provide a process for the preparation of a polyester dispersion suitable for use in a toner product that is more efficient, takes less time, with foam control, and results in a consistent toner product.